1. Field of the Invention
The present invention relates to a technique of receiving a broadcast signal and playing back broadcast program information based on the received broadcast signal.
2. Description of the Related Art
The infrastructure for broadcasting has recently shifted to the infrastructure for digital broadcasting. Along with this shift, high-definition digital broadcasts have been generally viewed. This allows people in homes to enjoy high-quality videos.
Broadcasting is regulated to perform white balance adjustment by adjusting the ratios of R, G, and B so as to match white with a standard color temperature in accordance with illumination conditions in a capturing location and to provide the resultant broadcast programs to homes.
As described above, it is known that when a video is to be captured by using a camera which captures still images, a video camera, or the like, white balance is adjusted in accordance with the state of a light source in a capturing location.
For example, as shown in FIG. 6, the average color temperature of sunlight on a fine day is about 5,000K, and that of sunlight on a cloudy day is about 7,000K. It is said that light fixtures have their own color temperatures, and the color temperatures of an incandescent lamp and fluorescent lamp are about 3,000K and 4,500K, respectively. FIG. 6 shows color temperatures under various circumstances.
When the human sees the colors of objects under such a light source, he/she sees the colors while automatically correcting the influences of ambient light. For this reason, the colors of objects which the human sees do not dramatically change even with changes in illumination light.
A video camera or the like using a CCD or a camera tube, however, records the color of an object as it is, and hence a captured video will reflect the color temperature of the light source. That is, if a video camera adjusted to daylight (6,500K) captures an image of a white object without any change under a fluorescent lamp, the captured image becomes bluish. The user has a strange feeling about the image capturing result.
For this reason, a video camera records images upon adjusting the ratios of signals from an image sensing device in accordance with the color temperature of an illumination light source so as to capture an image of a white object as a white image under the illumination.
If the above white balance adjustment has been done, white is defined by equal R, G, and B values.
The color which the human actually perceives as white is not indicated by one point on a chromaticity diagram, and the human recognizes a color close to blackbody radiation as white.
According to television standards such as the NTSC or high-definition (HD) standards, standard white is defined by 6,744K or D65 (6,504K).
That is, if the display color temperature of a transmitted signal (white signal) representing white is set to 6,500K on the television side, the user observes the white signal as white at 6,500K. If such a signal is set to 9,000K, the user observes the signal as white at 9,000K.
Concerning actual television viewing, there is a requirement that color adjustment be performed in accordance with user preference.
In order to meet such user requirement, a general display device is equipped with a function of allowing the user to change adjustment values of hue, color temperature, contrast, sharpness, and the like by, for example, on-screen display (OSD).
Such an apparatus is also equipped with a function of allowing the user to view a broadcast program in a state set by a manufacturer by selecting one of various viewing modes such as a cinema mode, a dynamic mode, and a living mode which are prepared in advance, instead of individually adjusting each adjustment item.
With a recognition that it is troublesome for users to perform the above adjustment for each broadcast program, there has recently been proposed an apparatus, as a receiver function, which performs correction such as color temperature correction, sharpness correction, and various kinds of color correction in accordance with the category of a viewed broadcast program (patent reference 1: Japanese Patent Laid-Open No. 2004-032000).
This apparatus sets an image quality and sound matching the category of a viewed broadcast program selected from an electronic program guide (EPG), which is detected as, for example, “sports”, “movie”, or “music”.
In addition, a product designed to manually designate a category has been on sale. A known product, for example, makes the color green vivid in golf broadcasting or changes the contrast characteristic of display in a broadcast of a skiing activity or the like.
As described above, there is a requirement that television viewing be done with adjustment values matching contents.
Assume that when a lighting in a given capturing location is an incandescent lamp (3,000K), white balance adjustment for a video camera is performed as it is, and a standard gray chart under the lighting is adjusted to output R, G, and B signals at the same ratios.
Assume that a video captured by such a video camera is displayed on a TV set adjusted to 6,500K and a TV set adjusted to 9,000K, and the user views the video on the respective TV sets. In this case, the user observes the video with different color appearances. In addition, this user observes the video in a color under a lighting different from the actual lighting.
Conventionally, in television broadcasting, for so-called real videos, they are broadcast with standard colors, and a TV viewer performs color adjustment and the like in accordance with his/her memories of colors, because the viewing environment of the TV viewer cannot be grasped.
In addition, each user individually performs color adjustment because of lack of basic guidelines or the like, and hence the color tones of viewed videos often differ from those captured.
Broadcast contents should differ in color tone depending on the broadcasting locations.
Consider a baseball broadcast or the like. In this case, different baseball stadiums have different types of lighting equipment, and light differs in state depending on the type of baseball stadium, i.e., whether the baseball stadium is a domed or open stadium.
Even if color correction is performed for each category in such a state as in the prior art, since the illumination conditions in the respective capturing locations differ from each other, optimal correction cannot be performed.
Furthermore, even if a viewer tries to perform adjustment in accordance with the original color tones, since there is no means available to make such adjustment, a viewed video does not reproduce real colors and considerably differs from the actual object.